Barometers: Aneroid Barometer
What is a Barometer?
A barometer is a scientific instrument used to measure atmospheric (barometric) pressure and give an indication of fair or poor weather.
How does an Aneroid Barometer work?
Invented in 1844 by French scientist Lucien Vidi, the aneroid barometer measures air pressure without using any liquids. Instead, it uses a small, flexible metal box called an aneroid cell (capsule), which is made from an alloy of beryllium and copper. The evacuated capsule (or usually several capsules, stacked to add up their movements) is prevented from collapsing by a strong spring. Small changes in external air pressure cause the cell to expand or contract. driving mechanical levers so that the tiny movements of the capsule are amplified and displayed on the face of the aneroid barometer. High barometric pressure supports sunny, clear, and favorable weather conditions; lower levels promote rainy and cloudy weather conditions. Many models include a manually set needle which is used to mark the current measurement so a change can be seen.
(www.wikipedia.com)
Is it OK to tap a barometer?
It is highly advisable to lightly tap the glass near the center brass knob with your fingers before taking a barometer reading. The light tap will overcome any friction that may affect accurate hand readings, especially during periods of slow atmospheric changes.
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